Amine salts of dithiophosphoric acids

ABSTRACT

Lubricating oil compositions containing as antiwear and detergent-inhibitor additives therein, an amine neutralized derivative of a dithiophosphoric acid prepared by reacting a long chain alkenyl-substituted C3-C8 monocarboxylic acid of 400-3,000 molecular weight with a primary or secondary hydrocarbylol amine, reacting the resultant amide with a phosphorus sulfide and neutralizing the resultant dithiophosphoric acid with a polyamino compound.

United States Patent I 3,546,324 AMINE SALTS OF DITHIOPHOSPHORIC ACEDSKurt Pollak, Westfield, N.J., assignor to Esso Research and EngineeringCompany, a corporation of Delaware No Drawing. Filed May 11, 1967, Ser.No. 637,646 Int. Cl. C07d 105/04; C07f 9/16; C10rn 7/46 U.S. Cl. 260-9257 Claims ABSTRACT OF THE DISCLOSURE Lubricating oil additives havingantiwear and detergent-inhibitor properties are prepared by P 8 treatingthe reaction product of a high molecular weight carboxylic acid, e.g.polyisobutenyl propionic acid, with an aminohydroxy compound, e.g.2,2'-iminodiethanol, and neutralizing the thus produced dithiophosphoricacid with a mono or polyamine.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to a lubricant additive composition which comprises aminederivatives of dithiophosphoric acid compounds. More particularly, theinvention pertains to oil-soluble amine derivatives of dithiophosphoricacid compounds prepared from P 5 treated hydroxy-containing amidesproduced by reacting a high molecular Weight carboxylic acid with ahydroxy-containing amine. In another aspect, the invention is concernedwith lubricant compositions containing small amounts of adithiophosphoric acid neutralized with an amine wherein thedithiophosphoric acid is prepared by P 8 treating aN-(hydroxy-containing hydrocarbyl) alkenyl-substituted monocarboxylicamide.

Description of the prior art Lubricants for modern high compressionpiston type internal combustion engines are required to have highdetergency, efficient sludge dispersing action and high 0xidationresistance in order that those engines will be kept free of varnish,sludge and coke-like deposits. In other words, a heavy duty detergenttype lubricating oil must be employed in such engines in order tomaintain a high degree of engine cleanliness and thus promote enginelife.

In the past, the majority of detergents, sludge dispersants andantioxidant materials that have been developed for use in lubricatingoils for internal combustion engines have been metallic derivatives,particularly alkaline earth metal sulfonates, alkaline earth metal saltsof alkyl phenol sulfides, colloidal dispersions of metallic carbonates(particularly alkaline earth metal carbonates), and the like. While, ingeneral, additives of these types have proved to be quite satisfactoryin their function as sludge dispersants and detergents, in manyinstances the ash content of these additives has presented adisadvantage in that the ash tends to accumulate in the combustionchamber of the engine to thereby cause preignition, spark plug fouling,valve burning and similar undesirable conditions. For this reason, aneffective dispersant that is ashfree is preferable over an ash-formingdetergent additive such as an alkaline earth metal salt of the typesmentioned above. Ashfree dispersants are also of advantage in motorfuels, fuel oil compositions, and diesel fuels.

3,546,324 Patented Dec. 8, 1970 ice It has now been found, in accordancewith the present invention, that certain amine derivatives ofdithiophosphoric acid compounds function as effective ash-free anti-Wear and detergent-inhibitor additives in lubricating oils. Broadly, theadditive of this invention is a dithophosphoric acid neutralized with amonoor polyamine wherein the dithiophosphoric acid is prepared by P 8treating a N- (hydroxy containing hydrocarbyl) alkenyl substituted C -Cmonocarboxylic amide. The hydrocarbyl referred to is a hydrocarbonradical selected from the group consisting of alkyl, cycloalkyl, aryl,and alkylaryl containing from 1 to 30 carbon atoms, preferably 1 to 12carbon atoms. The hydrocarbyl may also include alkoxyalkyl, alkoxyaryl,iminoalkyl and iminoaryl C -C radicals, i.e., those radicals having theformula: (R-X) R-X-R wherein X represents oxygen or nitrogen, nrepresents an integer ranging from 0 to about 10 and R represents analkyl and/or aryl group of the type immediately following. Specificexamples of hydrocarbyl groups include, among others, methyl, ethyl,butyl, hexyl, decyl, dodecyl, phenyl, tolyl, nphthyl, biphenyl,cyclohexyl, ethylcyclohexyl, cycloheptyl, methylcycloheptyl,ethoxyethyl, butoxybutyl, p-methoxyphenyl, etc. A preferred amide isN-(hydroxy-containing C -C alkyl) alkenyl-substituted C -Cmonocarboxylic amide. Even more preferred is N- di(hydroxy-containing CC alkyl) alkenyl-substituted C C monocarboxylic amide. The alkenyl groupreferred to is C -C olefin polymerized to a molecular Weight of400-3000.

The N-(hydroxy-containing hydrocarbyl) alkenyl-substituted C -Cmonocarboxylic amide is prepared by simple reaction between ahydroxy-containing amine and an alkenyl-substituted C -C monocarboxylicacid under conditions of amide formation. Typically, the alkenyl groupis a polymer of a C C monoolefin, e.g. polyethylene, polypropylene,polyisobutylene, polybutene, polyamylene, ethylene-propylene copolymer,propyleneisobutylene copolymer, etc., wherein the olefin polymer has anumber average molecular weight within the range of from about 400 toabout 3000. Especially useful products are obtained when the alkenylgroup is polyisobutenyl having a molecular Within the range betweenabout 700 and 1200.

In general, the aforedescribed alkenyl-substituted C -C monocarboxylicacid may be derived from an alpha-betaunsaturated monocarboxylic acid offrom 3 to 8 carbon atoms and the aforedescribed C C monoolefin polymerin accordance with well-known techniques. For example, the C Cmono-olefin polymer may be halogenated with either bromine or chlorine,preferably the latter, using sufiicient halogen to provide about one totwo atoms per molecule of the olefin polymer. Halogenation can beeffected at a temperature within the range from about ordinary ambienttemperatures to about 250 F. To aid in the halogenation step, thepolymer may be dissolved in a suitable solvent, such as carbontetrachloride, although the use of such a solvent is not necessary. Thetime required for halogenation may be varied to some extent by the rateat which the halogen is introduced. Ordinarily from about 2 to about 5hours is a satisfactory halogenation period. In a representative plantscale operation involving the chlorination of polyisobutylene of 830molecular weight, a pound batch will be chlorinated with 10 pounds ofchlorine introduced into the reactor over a period of 3 /2 hours with achlorination temperature of about 250 F.

The halogenated polymer thus obtained is condensed with an alpha,beta-unsaturated, monocarboxylic acid of from 3 to 8 carbon atoms.Ordinarily, because of their greater availability, acids of this classhaving 3 or 4 carbon atoms will be used. Such acids include acrylicacid, alpha-methylacrylic acid (i.e. 2-methyl propenoic acid) andcrotonic or isocrotonic acid (beta-methacrylic acid). Other alpha,beta-unsaturated acids that may be employed include tiglic acid (alpha,methylcrotonic acid), angelic acid (alpha-methylisocrotonic acid),sorbic acid, and cinnamic acid.

In an alternate preparation the halogenated polymer may be condensedwith an ester of the C to C unsaturated monocarboxylic acid, e.g., ethylmethacrylate, in place of the free acid. The esters that may be used inthis alternate preparation are those of aliphatic alcohols having from 1to carbon atoms, including methyl, ethyl, isopropyl, isobutyl, amyl,hexyl Z-ethyl hexyl decyl, and C oxo alcohols. Such esters include amylacrylate, isopropyl methacrylate, butyl crotonate, methyl acrylate, etc.In the subsequent amidation reaction an alcohol will be split out inplace of water. The higher boiling the alcohol, the more difficult willbe the removal of the alcohol from the reaction mixture. Generally,alcohols boiling above about 285 F. will not be desirable for thisreason. Furthermore, use of higher boiling alcohols represents aneconomic disadvantage in that excess Weights of materials are thus beingput into the reaction only to be removed later. Most preferably, theesters that will be used here are those of C -C aliphatic alcohols.

When the alkenyl substituted monocarboxylic acid is prepared bycondensing the halogenated polyolefin with the alpha, beta-unsaturatedacid or with an aliphatic ester thereof, at least one mole of acid orester is used per mole of halogenated polyolefin. Normally, the acid orits ester will be employed in excess and may amount to as much as 1.5 to2 moles per mole of halogenated polyolefin. The condensation temperaturemay be in the range of from about 300 to 500 F. and will more preferablybe within the range of from about 375 to 475 F. The condensationtemperature may require from about 3 to about 24 hours but willordinarily take place in from 6 to 18 hours. After the reaction has beencompleted, excess acid or ester may be purged from the mixture, forexample, by blowing with a stream of nitrogen at a temperature of 400 to500 F.

The present invention is not known to be dependent in any way on themethod of preparing the aforedescribed alkenyl-substituted carboxylicacid. Other methods for their preparation are well known to thoseskilled in the art. Consequently, such materials may be used regardlessof their source.

The aforedescribed alkenyl-substituted monocarboxylic acid is reactedWith a hydroxy-containing primary or secondary amine to produce anintermediate amide product which is subsequently P 8 treated. Aspreviously indicated, this intermediate product is aN-(hydroxy-containing hydrocarbyl) alkenyl-substituted monocarboxylicamide. Specific examples of suitable hydroxy containing primary aminesinclude, among others, ethanolamine, propanolamine, -amino-l-hexanol,S-amino-l-pentanol, aminocyclopentanols, aminocyclohexanols, o, m orpaminophenols, aminonaphthols, 2-(2-aminoethoxy) ethanol, 2-(2iminoethylamino) ethanol, etc. Non-limiting examples of suitablyemployed monohydroxy or dihydroxy secondary amines (i.e. monohydroxy ordihydroxy-containing imino compounds) include 2,2-iminodiethanol;1,1-iminodi-2-isopropanol; N,N-bis (4-cyclohexanol) amine; and4,4'-dihydroxydiphenylamine.

The alkenyl-substituted carboxylic acid and hydroxycontaining aminecompounds are reacted under conditions causing amide formation. Suchconditions are well known in the art, and it is not intended that theadditive of this invention be limited to any specific method ofpreparation. By way of example, the amide can be formed by reacting thecarboxylic acid and the hydroxy-containing amine compound in thepresence of a suitable solvent, e.g. neutral mineral oils, toluene,xylene, etc., at elevated temperatures, e.g. 230 F.450 F., andatmospheric pressure for a period of time ranging from about 4 to about24 hours.

The aforedescribed N- (hydroxy-containing hydrocarbyl)alkenyl-substituted amide is reacted with a phosphorus sulfide such asphosphorus pentasulfide, P 5 under conditions causing phosphorodithioicacid formation. The dithiophosphoric acid formation is effected by meanswell known in the art. For example, the P 8 may be reacted with a singlehydroxy-containing amide compound or mixtures of said compounds bymixing the reactants at a temperature of about to 175 0., preferably to160 C. using about 0.25 to about 0.50 moles of P 8 per alcohol group.The completion of the reaction may be noted visually and will beindicated by the dissolution of the P 5 The reaction time required wouldgenerally be in the range of about 0.5 to 24 hours, usually about 3 to 6hours. After the reaction is completed, the reaction is preferably blownwith nitrogen or other inert gas to remove hydrogen sulfide therefrom.If desired, the reaction may be carried out in a solvent such as amineral oil, toluene, xylene, etc.

The dithiophosphoric acid thus formed is neutralized with acyclic orcyclic, primary and secondary mono and poly amines containing from 1 toabout 24 carbon atoms. It is preferred, however, to use an aliphaticpolyamine having the following general formula:

wherein n is 2 to 3 and m is a number from 0 to 10. Specific compoundscoming within the formula include, among others, diethylene-triamine,tetraethylenepentamine, dipropylenetriamine, octaethylenenonamine, andtetrapropylenepentamine, N,N-di(2-amino-ethyl) ethylenediamine may alsobe used. Other aliphatic polyamino compounds that may be used areN-aminoalkyl-piperazines of the formula:

wherein X is a number 1 to 3, and R is hydrogen or an aminoalkyl radicalcontaining 1 to 3 carbon atoms. Specific examples includeN-(Z-aminoethyl) piperazine, N-(Z-aminoisopropyl) piperazine, andN,N'-di-(2-aminoethyl) piperazine.

The use of mixtures of alkylene polyamines, mixtures of N-aminoalkylpiperazines, and mixtures of the alkylene polyamines with theN-aminoalkyl piperazines is also contemplated, and the term aliphaticpolyamine is intended to embrace all of these materials.

Neutralization of the dithiophosphoric acid with the amine isconventionally effected, for example, by simple mixing of the reactantsat ambient temperatures and pressures.

The additive products of this invention may be incorporated inlubricating oil compositions in concentration ranges of from about 0.001to about 10 wt. percent and Will ordinarily be used in concentrations offrom about 0.1 to about 5 wt. percent. The lubricating oils to which theadditives of the invention may be added include not only minerallubricating oils, but synthetic oils also. The mineral lubricating oilsmay be of any preferred types, including those derived from the ordinaryparafi'lnic, naphthenic, asphaltic, or mixed base mineral crude oils bysuitable refining methods. Generally they will have a viscosity of 210F. of between about 45 and about 90 SUS (Saybolt Universal Seconds) andat 100 F. a viscosity of between about and about 1,100 SUS. Theviscosity indices of these oils will generally range between about andabout 100 or more. In the case of oils employed in high speed, heavyduty Diesel engines, oils of high viscosity indices are often preferred,i.e. of the order of 100 or higher, but usually most Diesel enginesemploy lubric'ating oils having viscosities of between about 75 andabout 80 SUS at 210 F. and at 100 F. of between about 800 and about1,250 SUS with viscosity indices ranging between about 55 and about 80.Synthetic hydrocarbon lubricating oils may also be employed. Thesesynthetic oils include, among others,dibasic acid esters such as di-2-ethyl hexyl sebacate, carbonate esters, phosphate esters, halogenatedhydrocarbons, polysilicones, polyglycols, glycol esters such as C oxoacid diesters of tetraethylene glycol, and complex esters as for examplethe complex ester formed by the reaction of 1 mole of sebacic acid with2 moles of tetraethylene glycol and 2 moles of 2 ethyl hexanoic acid.

'In the lubricant compositions of this invention, other conventionaladditives may also be present, including dyes, pour point depressants,antiwear agents, e.g. tricresyl phosphate, zinc dialkyl dithiophosphatesof 3 to 8 carbon atoms, antioxidants such as phenyl-alpha-naphthylamine,tertiary octylphenol sulfide, bis-phenols such as 4,4-methylene bis2,6-ditertiary butylphenol), viscosity index improvers such aspolymethacrylates, polyisobutylene, alkyl fumarate-vinyl acetatecopolymers, and the like, as well as other dispersants.

- It is within the contemplation of this invention to prepare additiveconcentrates in which the concentration of additive is greater thanwould normally be employed in a finished lubricant. These concentratesmay contain in the range of from 10 to 80% of additive on an activeingredient basis, the balance being a hydrocarbon solvent such as, forexample, a mineral oil. Such concentrates are convenient for handlingthe additive in the ultimate blending operation into a finishedlubricating oil composition. The additive concentrates may be made upsimply of an additive of the persent invention in a suitable mineral oilmedium or they may include other additives that are intended for usealong with the additives of the invention in a finished lubricant. Thus,if the additives are to be used in conjunction with conventionaldetergents, an additive concentrate can be prepared containing say 30 to60 wt. percent of an additive of the invention and 5 to 20 wt. percentof a metal sulfonate, e.g. calcium petroleum sulfonate from sulfonicacids of about 450 molecular weight, or a metal alkylphenol sulfide,e.g. calcium nonylphenol sulfide, with the balance being a minerallubricating oil.

Additionally, 5 to wt. percent of an antiwear agent such as zincdialkyldithiophosphate, e.g. mixed zinc lautyl and amyl dithiophosphatesmay also be present in the additive concentrate package.

The invention can be more fully understood by reference to the followingexamples.

EXAMPLE 1 This example serves to illustrate the preparation of apolyisobutenyl propionic acid.

A 110-pound portion of polyisobutylene of 780 molecular Weight (asdetermined by osmometry) was heated to 250 F., then a stream of chlorinewas passed through the heated polyisobutylene at the 250 F. temperatureat a rate of 2.5 pounds of chlorine per hour for a total of 4 hours, thetotal chlorine treat thus being 10 pounds. A sample of the chlorinatedproduct analyzed 4.3% chlorine and had an API gravity of 23.3. To thechlorinated polyisobutylene there was added 10.5 pounds of acrylic acid.Over a period of two hours the temperature was raised from 250 F. to 425F. and the pressure was increased to p.s.i.g. Heating was continued for5 hours at 425 F. and the reaction vessel was vented to maintain thepressure of 20 p.s.i.g. The pressure was then released and the mixturewas purged with nitrogen for 2 hours to remove unreacted acrylic acid.The polyisobutenyl pro- 6 pionic acid thereby obtained weighed 109.3pounds and had a total neutralization number (ASTM D664) of 46.2milligrams of KOI-I per gram. The chlorine content was found to be 0.3wt. percent.

EXAMPLE 2 An additive of this invention was prepared as follows:

Into a glass reaction vessel fitted with a mechanical stirrer, heatingmantle, thermometer and condenser containing 1,245 grams ofpolyisobutenyl propionic acid pro duced in the manner of Example 1(number average molecular weight 1245, ASTM Neut. No. 45) in 1,000 gramsof a solvent neutral mineral oil (150 SUS viscosity at F.) there werecharged grams of 2,2'-iminodiethanol. The resulting mixture was thenheated at about 300 F. for a period of about 16-18 hours. The reactionmixture was thereafter cooled to about F. whereupon 111 grams of P 5 wasadded over a period of about 15 minutes. Upon completion of the P 8addition, the mixture was heated at about 300 F. for about 4 hours. Themixture was then cooled to room temperature and 52.5 grams of diethylenetriamine was slowly added over a period of about 30 minutes. Afterstirring for 1 hour, the product was filtered through Dicalite in thecold. The final product recovered totaled 2322 grams of which 55 wt.percent was additive product, the remainder being the mineral oil.

EXAMPLE 3 The procedure of Example 2 is repeated, but instead of theirninodiethanol the polyisobutenyl propionic acid is reacted with 61grams of ethanol amine. The resulting hydroxy-containing amide productis then treated 'with 55.5 grams P S and thereafter reacted with thediethylenetriamine.

A number of routine tests were carried out on a typical base oilcontaining the novel additive hereinbefore described in order toillustrate the beneficial efiects derived therefrom. The following testswere performed:

(1) An Oxidation Stability Test was used for a laboratory evaluation ofthe antioxidant properties of the additive. This test involves heatingthe compounded oil to a temperature of about 340 F. in the presence of acopper-lead oxidation catalyst While intimately mixing the compoundedoil with air at the rate of 2 c.f./hr. The viscosity increase (SUS, at100 F.) after 23 hours is measured and a determination of the percentageof viscosity increase over that of the original unoxidized oil is made.

(2) A Copper-Lead Bearing Weight Loss, in milligrams, involving thecompounded oil was also conducted. The measure of the change in weightof the Cu-Pb catalyst in test (1) in milligrams is determined.

(3) The well-known Falex Test as described in, for example, US. SteelManual, Proposed Falex Machine Method ASTM D-2 Section V, Tech. k wasused to determine the antiwear properties of the novel additives.

(4) The Disc and Rider Test was also used to evaluate the antiwearproperties of the additives. In this test, a spinning (50 r.p.m.) steeldisc is contacted with a fixed steel ball (1.25 cm. dia.), and a load of500 g. is then impressed upon the disc. A film of oil is maintained onthe spinning disc at the point of contact with the steel ball. Aconstant electrical voltage is then applied be tween the spinning discand the steel ball. The resulting resistance is measured after 20minutes for tests employing the base oil with no additive and the baseoil containing an additive of this invention. The resistance recordedwhen employing the base oil alone was given a metallic contact of 100%,and other resistance readings were given proportionately higher or lowerpercent metallic contact, i.e. the resistance between the ball and discwas found to be proportional to the percent metallic contact with thehigher percent metallic contact giving the lower resistance.

A series of tests were carried out using a typical base oil containingvarious amounts of additive of this invention and prior art additives.The base oil can best be described as being a phenol extracted oilhaving a viscosity at 210 F. of 60 SUS and at 100 F. of 460 SUS. Theresults are given below in Tables I-III.

TABLE I.OXIDATION STABILITY TEST Percent CuPb viscosity bearing increaseweight,

Oil tested SUS loss, mg.

Base oil alone 85 143 Base oil plus 5.0 wt. percent of product ofExample 2 (55 wt. percent active ingredient) 8. G 27 Base oil plus 5.5wt. percent of PIBA/TEPA concentrate 2 110 330 Base oil plus 5.0 wt.percent of PIBA/TEPA con= densate 2 plus 0.5 wt. percent Ethyl 728 3 85223 Base oil plus 3 wt. percent of PIBA/TEPA condensate 2 plus 0.5 wt.percent Ethyl 728 plus 2.0 wt percent of product of Example 2 7. 2 28TABLE II Falex text (1) Oil tested: Mg. wt. loss Base oil alone FailureBase oil plus 2.0 wt. percent of Product of Example 2 (55 Wt. percentactive ingredient) 1.1 2 min. 250 lb. 8 min. 400 1b.

TABLE III.DISC AND RIDER TEST Ooefiicient Percent of friction, metallicOil tested 11 avg. contact Base oil alone 0. 148 100 Base oil plus 1.0wt. percent of product of Example 2 (55 wt. percent active ingredient)0. 116 65 It is seen from the data presented in Tables II and III thatthe additive of this invention is an efiective antiwear agent.

What is claimed is:

1. An amine neutralized derivative of a dithiophosphon'c acid preparedby reacting an alkenyl-substituted C -C monocarboxylic acid, wherein thealkenyl group is a polymerized C -C monoolefin having a molecular weightbetween about 400 and about 3000 with a pri mary or secondaryhydroXy-containing amine selected from the group consisting of monoanddi C -C alkylol amine, mono and diphenylol amine, mono cyclopentanolamine, mono and dicyclohexanol amine, to form the corresponding N(hydroxy-hydrocarbon) substituted amide, reacting the said amide withphosphorus pentasulfide and neutralizing the resultant dithiophosphoricacid with a polyamine having the formula:

wherein n is 2 to 3 and m is a number from 0 to 10.

2. An amine neutralized derivative of a dithiophosphoric acid as inclaim 1 wherein the hydroxy-containing amine is a C -C alkylol amine.

3. An amine neutralized derivative of a dithiophosphoric acid as inclaim 2 wherein the hydroxy-containing amine is diethylol amine.

4. An amine neutralized derivative of a dithiophosphoric acid as inclaim 1 wherein the alkenyl group has a molecular weight of betweenabout 700 and about 1200.

5. An amine neutralized derivative of a dithiophosphoric acid as inclaim 4 wherein the alkenyl group is polyisobutenyl of about 780molecular weight and the monocarboxylic acid is propionic acid.

6. An amine 'nuetralized derivative of a dithiophosphoric acid as inclaim 5 wherein the neutralizing polyamine is diethylene triamine.

7. An amine neutralized derivative of a dithiophosphoric acid as inclaim 6 wherein the hydroxy-containing amine is diethylol amine.

No references cited.

CHARLES B. PARKER, Primary Examiner A. H. SUTTO, Assistant Examiner US.Cl. X.R.

